Electronic fuel injection systems typically include a digital computer for monitoring a variety of engine operating parameters, engine conditions and throttle or power outputs signals from a throttle sensor to produce fueling signals in response thereto. The fueling signals are supplied to electromechanical fuel injection devices. A great variety of fuel injection systems are known in the art. A few of those systems are discussed below.
Hanafusa et al., U.S. Pat. No. 4,700,681, discloses a fuel injection system for an internal combustion engine wherein each cylinder of the engine includes an individual fuel injector. The Hanafusa et al. device calculates a basic amount of fuel necessary for one engine cycle, and then a final injection amount is calculated as a difference between the basic amount of fuel required with respect to the actual amount of fuel injected during a preceding injection of the corresponding group of cylinders, which are grouped according to a phase relationship in view of the angular position of the crankshaft. Klassen, U.S. Pat. No. 4,869,222, discloses a control system and method for controlling actual fuel delivered by individual fuel injectors. A plurality of fuel command controllers provide a separate command signal to each fuel injector in response to a single base fuel command. The correction time period is calculated during a correction interval and each of the fuel command signals is offset in a predetermined sequence by a predetermined amount. Measurements of the average air/fuel ratios among the combustion chambers is taken during each correction interval. Air flow into the combustion chambers is also measured. In response to these measured parameters, the actual fuel delivered to each fuel injector is calculated. Ohnari et al., U.S. Pat. No. 4,887,216, discloses a method of engine control timed to engine revolution. Controlled measurement timings of air volume as well as fuel volume and exhaust gas parameters are included in calculating timing of fuel injection volume and ignition timing. These timings are synchronized with regard to a crank angle position such as top dead center. Nakamura et al., U.S. Pat. No. 4,825,373, discloses a fuel injection timing control apparatus for a diesel engine, including a determination of when actual ignition can be detected. The apparatus includes means for computing the target time at which injection should occur and means for sensing when injection actually occurs with respect to a reference crankshaft position. Feedback control means enable adjustment of the actual injection time to bring the previously mentioned parameters into coincidence with the target injection time. A compensation factor is computed based upon the difference between the actual and target firing times, and is utilized to modify the actual fuel injection timing so as to bring the actual and target firing times into coincidence. Oshizawa, U.S. Pat. No. 4,825,369, discloses an apparatus for controlling fuel injection timing of a fuel injection pump. The Oshizawa device includes a device for detecting a delay time of fuel injection due to the delay time of a solenoid valve which is opened/closed by a driving pulse. The solenoid valve controls fuel injection. The delay time of fuel injection is converted into the angle of a driving shaft of the pump corresponding to the delay time. A target advance angle according to the operating condition of an associated internal combustion engine is calculated and the output timing of the driving pulse is set by taking a count of the angle corresponding to the delay time of fuel injection, whereby the target advance angle can be obtained in response to the driving pulse.
As is shown in the above patents, various feedback control systems have been devised to provide rapid and responsive control of fuel injection systems used with internal combustion engines. With regard to heavy duty diesel engines, a primary objective with regard to a feedback control system for controlling fuel injection is economy. In addition, responsiveness to driver inputs for variations in power output of the engine must be rapid and responsive in a real time sense. A fuel injection system which provides instantaneous changes in fuel injection control signals would decrease delays in the fuel injection system resulting in improved fuel economy as well as improved responsiveness to driver throttle commands.